Oxide cathode



y sept.v 3o, 1930.

FiledI Feb. 25, 1927 .Maha/mes fa/yhes @dented Sept.v 30, 1930 UNITED STATES .PATEN- oli-inc -v tmzss JOHANNES BBUIJNES, JACOB VAN DER HOEVEN, AND EKXO OOSTERHUIS, F EINDHOVEN,

NETHERLANDS, ASSIGNOVRS TO N. V. PHILIPS GLOEILAMPEN-FABRIEKEN, 0F EIND- HovEN, NETHERLANDS, A LIMITED LI ABILITY COMPANY OXIDE CATEJDE Application Med February 25, 1927, Serial No. 171,051, and in the Netherlands April B, 1926.

crease the current of electrons emitted bv van incandescent cathode per unitof length.

@ther objects will appear from the following description of the invention, made g with reference to the accompanying drawing which shows an embodiment of an incan-I descent cathode according to the invention.

rlheincandescent cathode according`- to the invention has a core of highly refractory e@ metal, preferably a poor conductor of heat,

on which is helically wound another metal wire having applied to ita substance of high emitting capacity.

it is preferable that an element selected from .the lefthand members of Group Vl of the periodic system between atomic numbers lil and 75 for example, in the form of a wire, be used for the core a metal wire which is preferably coated with alkaline earth oxide, being then wound on the said core so as to be in electrical Contact therewith. Preferably platinum or a platinum alloy is used for the winding wire. ln the drawing a stretched core wire l made, for example, of tungsten or molybdenum has helically wound onit a wire 2. The turns of the latter wire may be adjacent each other, as shown in the drawing but also they may be wound quite well so as to heslightl spaced apart,it` this should he desirable or any reason, forexample, in view or" the steepness of the discharge tube for which the cathode is intended.V

The wire 2 which is preferably lmade oi platinum or a platinum alloy (forexample platinum-rhodium) isv coated with a lm of a Y substance of high emission capacity, for example barium oxide. rlfhis oxide may be applied to the wire 2 in one of the ways known for this purpose, for example, by first coating the wire with copper, oxidizing the copper and precipitating metallic barium on the copper oxide. The barium reduces the copper in the-presence of heat and by additional heat the reduced'copper is evaporated,

leaving barium oxide on the wire. The wire 2 may be coated with copper and oxidized before it is wound on the core l andonly then the barium may be precipitated.

ln the example illustrated the core wire 1T extends on both sides outside the ends of the wire spiral 2 and the ends of the wire 2 are secured to the said protruding ends of the core wire 1, which ,are finally attached to leads 3 and 4 which serve tosupply the current and which are secured in a knownman# ner to the glass pinch of a lamp toot.

However, it is also possible to make the core wire with the emission wire wound on it in continuous len ths, to divide it into portions of the required length and to set the said portions tightly between the leads. The example illustrated has, however, the advantage that the temperature will he substantially uniform all along the emitting surface by reason of the comparatively poor conduction of heat on the part of the free ends of the core wire l. When the incandescent cathode is used in a discharge talee comprising one or more auxiliary electrodes9 the so-called steepness is flunced.

. ""9 at we claim is:

i. An incandescent cathode comprising a core of highly refractory metal, a metal wire helically wound on the said core so as to be in electrical contact therewith, and a sub'- stance of high electron emitting capacity applied to said wire.

thus favourably in- 2. An incandescent cathode, comprising a ap lie and a substance of high electron emitting core consisting of at least one of t e metals tungsten and molybdenum, a platinum Wire helically wound on the core so as to be in electrical contact therewith, and a substance of high electron emitting capacity comprisin g an alkaline earth oxide applied to said wire.

5. An incandescent cathode, comprising a core consisting of an element of the left hand members of Group VI of the periodic system between atomic numbers 41 and 75, a metal wire helically wound on the core so as to be in electrical contact therewith, and a substance of high electron emitting capacity comprising an alkaline earth oxide applied to said wire. i

` 6. An incandescent cathode comprising a core consisting of an element of the left hand members of Group VI of the periodic system between atomic numbers 41 and 75, a metal wire comprising platinum helically wound on the core so as to be in electrical contact therewith, and a substance of high electron emitting capacity comprising an alkaline earth oxide applied to said Wire.

7. An incandescent cathode comprising a core consisting of an element/of the left hand members of Group VI of the periodic system between atomic numbers 41 and 75, a platinum wire helicall wound on the core so as to be in electrica contact therewith, and a substance of high electron emitting capacity comprising an alkaline earth oxide to-said wire. Y

n testimon whereof We afiix our signatures, at the c1ty`of Eindhoven, this 4th day February, A. D. .1927. i f

JOHANNES BRUIJNES. JACOB VAN DER HOEVEN. EKKO OOSTERHUIS.

vmesi- AlMER 1,777,253.-Johamtes Bruijnes, Jacob van der Hoeven, and Ekko Oosterhuis, Eindhoven,

' llen thof'thewire. k[jieal GazetteAugust 9, 1932.]

Netherlands. OXIDE CA'rHoDE. Patent dated September 30, 1930. Disclaimer filed July 13, 1932, by the assignee, N. V. Philips Gloez'lampenjabrieken.

Hereby enters this disclaimer to those parts of certain claims in saidspecification which are in the following words, to Wit:

In the claims, where the language a Wire helically wound on the core so as to be in v'electrical contact therewith 1s employed, your petitioner disclaims ythe use of any construction other than Where the Wire is shorted directly on' the core throughout the 

